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<td class="header">&nbsp; Back Geocoding<br>
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<h3>Sentinel-1 Back Geocoding</h3>
<p class="MsoNormal"><span>This operator co-registers two S-1 SLC
split products (master and slave) of the same sub-swath using the
orbits of the two products and a Digital Elevation Model
(DEM).<br>
</span></p>
<p class="MsoNormal"><span></span>In resampling the slave images into master
frame, deramp and demodulation are performed first to the slave image,
then the truncated-sinc interpolation is performed. Finally, the reramp
and remodulation are applied to the interpolated slave image. <br>
<span style=""></span></p>
 
<h4>Input <br>
</h4>


<ul>
  <li>Before running this operator, user should first run S-1 TOPS
Split operator to both master and slave products to get the same
sub-swath and same polarization data for co-registration (e.g. IW1 -
VV). <br>
  </li>
  <li>The user should run Apply Orbit File to correct the orbits in
both the split products with the Sentinel Precise (or Restitude) orbit
files. This step can be skipped if no precise or restitude orbit file
is available. Otherwise this step is always recommended in order to
achieve better co-registration result.<br>
  </li>
</ul>
<h4>Output <br>
</h4>



<ul>
  <li>The output of the operator are the co-registered master and slave bands in I/Q format. <br>

  </li>
</ul>

<h4>Parameters Used<br>
</h4>



<ul>
  <li>Digital Elevation Model: The DEM type. Currently the following DEMs are supported<br>
  </li>
  <ul>
    <li>ACE2_5min</li>
    <li>ACE30</li>
    <li>ASTER 1sec GDEM<br>
    </li>
    <li>GETASSE30</li>
    <li>SRTM 1Sec Grid</li>
    <li>SRTM 3Sec</li>
    <li>user provided external DEM file<br>
    </li>
  </ul>
  <li>DEM Resampling Method: Interpolation method for obtaining elevation values
        from the original DEM file. The following interpolation methods are available</li>
  <ul>
    <li>nearest neighbour</li>
    <li>bi-linear</li>
    <li>cubic convolution</li>
    <li>5-points bi-sinc</li>
    <li>11-points bi-sinc</li>
    <li>21-points bi-sinc</li>
    <li>bi-cubic<br>
    </li>
  </ul>
  <li>Resampling
Type: Interpolation methods for obtaining pixel values from the source
image. The interpolation methods available are the same as listed
above. Generally the accurate 21-point truncated sinc interpolation is
encouraged to use for complex image interpolation. This, of course,
will take longer processing time than using other interpolation method.
With other interpolation method, however, some oscillation effect could
be introduced in the interpolated image and in the coherence image
generated later on. &nbsp;</li>
  <li>Mask out areas with no elevation:&nbsp; Checkbox indicating if
areas without elevation should be masked out from co-registration. It
is recommended to select this checkbox to avoid artefacts along the
coast in the co-registered images.<br>
  </li>
  <li>Output Deramp and Demod Phase: Checkbox indicating if deramp and
demodulation phases should be output as separated bands. This option is
mostly for debugging purpose and not recommended for most users.</li><li>Disable
Reramp: Checkbox indicating if deramped and demodulated master and
slave bands should be output. This option should not be selected if the
coregistered master and slave bands will be used in generating
interferogram. </li>
</ul>

<p><img style="width: 636px; height: 491px;" alt="" src="images/backgeocodingUI.jpg"><br>
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